1. Field of the Invention
The present invention relates to gasoline compositions suitable as automotive fuels. In particular, the invention concerns gasoline compositions containing hydrocarbons derived from renewable hydrocarbon sources and methods of producing such gasolines. The present invention also relates to a method of reducing the emissions of one or more pollutants, selected from the group consisting of unsaturated and aromatic compounds, such as diolefines and benzene, from an automotive engine.
2. Description of Related Art
Ethanol is the dominant liquid biofuel globally at present. This is at least partly because it is readily available. The most common process for producing bioalcohols (i.e. alcohols obtained from renewable sources) is by fermentation of a sugar-type feedstock using yeast. Alternative routes for converting various biomasses to bioalcohols include thermochemical processing, for example biomass gasification followed by alcohol synthesis, or gasification followed by fermentation using anaerobic bacteria.
There are a number of studies on the effects of low-concentration ethanol additions on exhaust emissions. Ethanol generally has a positive impact on CO and HC tailpipe emissions. Conversely, NOx emissions tend to increase when ethanol is added to gasoline. The ozone-forming potential tends to increase with ethanol/gasoline blends due to the increased evaporative, acetaldehyde and NOx emissions. The ethanol content of fuel does not generally influence benzene and 1,3-butadiene emissions. Particulate matter emissions from gasoline-fuelled cars are typically low. The major drawback of adding ethanol to gasoline is an increase in emissions of acetaldehyde, which is classified as a harmful “air-toxic” substance. A catalyst can efficiently remove aldehyde emissions, but not in all conditions, for example during a cold start.
The European Union requires biofuels to achieve at least a 10% share of transport energy by 2020, and even higher shares are being attempted regionally.
The use of ethanol in conventional gasoline cars is generally limited to 10-15 v/v % (vol.-%, approx. 7-10 as an energy equivalent percentage) due to technical restrictions. Fuels with an oxygen content higher than approx. 4 m/m % are not necessarily compatible with conventional spark-ignited cars. Today, higher ethanol blending ratios are therefore possible only by using Flexible Fuel Vehicle (FFV) technology designed to use any proportion of, for example, ethanol and gasoline in the blend.
Present conventional cars will, however, continue to take the major share of gasoline car fleets for the next 10 to 20 years at least, and it is therefore necessary to establish and assess alternative biocomponent options for them.